Homemade natural air freshener?

Help me. I've got a little boy recovering from a stomach flu and a big boy recovering from knee surgery. Let's just say that two of our bedrooms could use a little, er, air freshening. Opening the windows on this cold, rainy day is not my first choice (or theirs), and I don't think my usual remedy of boiling ground cinnamon and cloves on the stovetop will reach these rooms.

How do you freshen up bedrooms naturally? A little citrus action? Essential oils? Thanks for any tips you can offer!